2 * ----------------------------------------------------------------------------
3 * "THE BEER-WARE LICENSE" (Revision 42):
4 * <phk@FreeBSD.ORG> wrote this file. As long as you retain this notice you
5 * can do whatever you want with this stuff. If we meet some day, and you think
6 * this stuff is worth it, you can buy me a beer in return. Poul-Henning Kamp
7 * ----------------------------------------------------------------------------
10 #include <sys/cdefs.h>
11 __FBSDID("$FreeBSD$");
15 #include <sys/param.h>
16 #include <sys/kernel.h>
17 #include <sys/sysctl.h>
18 #include <sys/syslog.h>
19 #include <sys/systm.h>
20 #include <sys/timepps.h>
21 #include <sys/timetc.h>
22 #include <sys/timex.h>
25 * A large step happens on boot. This constant detects such steps.
26 * It is relatively small so that ntp_update_second gets called enough
27 * in the typical 'missed a couple of seconds' case, but doesn't loop
28 * forever when the time step is large.
30 #define LARGE_STEP 200
33 * Implement a dummy timecounter which we can use until we get a real one
34 * in the air. This allows the console and other early stuff to use
39 dummy_get_timecount(struct timecounter *tc)
46 static struct timecounter dummy_timecounter = {
47 dummy_get_timecount, 0, ~0u, 1000000, "dummy", -1000000
51 /* These fields must be initialized by the driver. */
52 struct timecounter *th_counter;
53 int64_t th_adjustment;
55 u_int th_offset_count;
56 struct bintime th_offset;
57 struct timeval th_microtime;
58 struct timespec th_nanotime;
59 /* Fields not to be copied in tc_windup start with th_generation. */
60 volatile u_int th_generation;
61 struct timehands *th_next;
64 static struct timehands th0;
65 static struct timehands th9 = { NULL, 0, 0, 0, {0, 0}, {0, 0}, {0, 0}, 0, &th0};
66 static struct timehands th8 = { NULL, 0, 0, 0, {0, 0}, {0, 0}, {0, 0}, 0, &th9};
67 static struct timehands th7 = { NULL, 0, 0, 0, {0, 0}, {0, 0}, {0, 0}, 0, &th8};
68 static struct timehands th6 = { NULL, 0, 0, 0, {0, 0}, {0, 0}, {0, 0}, 0, &th7};
69 static struct timehands th5 = { NULL, 0, 0, 0, {0, 0}, {0, 0}, {0, 0}, 0, &th6};
70 static struct timehands th4 = { NULL, 0, 0, 0, {0, 0}, {0, 0}, {0, 0}, 0, &th5};
71 static struct timehands th3 = { NULL, 0, 0, 0, {0, 0}, {0, 0}, {0, 0}, 0, &th4};
72 static struct timehands th2 = { NULL, 0, 0, 0, {0, 0}, {0, 0}, {0, 0}, 0, &th3};
73 static struct timehands th1 = { NULL, 0, 0, 0, {0, 0}, {0, 0}, {0, 0}, 0, &th2};
74 static struct timehands th0 = {
77 (uint64_t)-1 / 1000000,
86 static struct timehands *volatile timehands = &th0;
87 struct timecounter *timecounter = &dummy_timecounter;
88 static struct timecounter *timecounters = &dummy_timecounter;
90 time_t time_second = 1;
91 time_t time_uptime = 1;
93 static struct bintime boottimebin;
94 struct timeval boottime;
95 static int sysctl_kern_boottime(SYSCTL_HANDLER_ARGS);
96 SYSCTL_PROC(_kern, KERN_BOOTTIME, boottime, CTLTYPE_STRUCT|CTLFLAG_RD,
97 NULL, 0, sysctl_kern_boottime, "S,timeval", "System boottime");
99 SYSCTL_NODE(_kern, OID_AUTO, timecounter, CTLFLAG_RW, 0, "");
100 SYSCTL_NODE(_kern_timecounter, OID_AUTO, tc, CTLFLAG_RW, 0, "");
102 static int timestepwarnings;
103 SYSCTL_INT(_kern_timecounter, OID_AUTO, stepwarnings, CTLFLAG_RW,
104 ×tepwarnings, 0, "");
107 #define TC_STATS(foo) \
109 SYSCTL_UINT(_kern_timecounter, OID_AUTO, foo, CTLFLAG_RD, &foo, 0, "");\
112 TC_STATS(nbinuptime); TC_STATS(nnanouptime); TC_STATS(nmicrouptime);
113 TC_STATS(nbintime); TC_STATS(nnanotime); TC_STATS(nmicrotime);
114 TC_STATS(ngetbinuptime); TC_STATS(ngetnanouptime); TC_STATS(ngetmicrouptime);
115 TC_STATS(ngetbintime); TC_STATS(ngetnanotime); TC_STATS(ngetmicrotime);
118 #define TC_COUNT(var) var++
121 #define TC_COUNT(var) /* nothing */
122 #endif /* TC_COUNTERS */
124 static void tc_windup(void);
125 static void cpu_tick_calibrate(int);
128 sysctl_kern_boottime(SYSCTL_HANDLER_ARGS)
133 if (req->flags & SCTL_MASK32) {
134 tv[0] = boottime.tv_sec;
135 tv[1] = boottime.tv_usec;
136 return SYSCTL_OUT(req, tv, sizeof(tv));
139 return SYSCTL_OUT(req, &boottime, sizeof(boottime));
143 sysctl_kern_timecounter_get(SYSCTL_HANDLER_ARGS)
146 struct timecounter *tc = arg1;
148 ncount = tc->tc_get_timecount(tc);
149 return sysctl_handle_int(oidp, &ncount, 0, req);
153 sysctl_kern_timecounter_freq(SYSCTL_HANDLER_ARGS)
156 struct timecounter *tc = arg1;
158 freq = tc->tc_frequency;
159 return sysctl_handle_quad(oidp, &freq, 0, req);
163 * Return the difference between the timehands' counter value now and what
164 * was when we copied it to the timehands' offset_count.
166 static __inline u_int
167 tc_delta(struct timehands *th)
169 struct timecounter *tc;
172 return ((tc->tc_get_timecount(tc) - th->th_offset_count) &
173 tc->tc_counter_mask);
177 * Functions for reading the time. We have to loop until we are sure that
178 * the timehands that we operated on was not updated under our feet. See
179 * the comment in <sys/time.h> for a description of these 12 functions.
183 binuptime(struct bintime *bt)
185 struct timehands *th;
188 TC_COUNT(nbinuptime);
191 gen = th->th_generation;
193 bintime_addx(bt, th->th_scale * tc_delta(th));
194 } while (gen == 0 || gen != th->th_generation);
198 nanouptime(struct timespec *tsp)
202 TC_COUNT(nnanouptime);
204 bintime2timespec(&bt, tsp);
208 microuptime(struct timeval *tvp)
212 TC_COUNT(nmicrouptime);
214 bintime2timeval(&bt, tvp);
218 bintime(struct bintime *bt)
223 bintime_add(bt, &boottimebin);
227 nanotime(struct timespec *tsp)
233 bintime2timespec(&bt, tsp);
237 microtime(struct timeval *tvp)
241 TC_COUNT(nmicrotime);
243 bintime2timeval(&bt, tvp);
247 getbinuptime(struct bintime *bt)
249 struct timehands *th;
252 TC_COUNT(ngetbinuptime);
255 gen = th->th_generation;
257 } while (gen == 0 || gen != th->th_generation);
261 getnanouptime(struct timespec *tsp)
263 struct timehands *th;
266 TC_COUNT(ngetnanouptime);
269 gen = th->th_generation;
270 bintime2timespec(&th->th_offset, tsp);
271 } while (gen == 0 || gen != th->th_generation);
275 getmicrouptime(struct timeval *tvp)
277 struct timehands *th;
280 TC_COUNT(ngetmicrouptime);
283 gen = th->th_generation;
284 bintime2timeval(&th->th_offset, tvp);
285 } while (gen == 0 || gen != th->th_generation);
289 getbintime(struct bintime *bt)
291 struct timehands *th;
294 TC_COUNT(ngetbintime);
297 gen = th->th_generation;
299 } while (gen == 0 || gen != th->th_generation);
300 bintime_add(bt, &boottimebin);
304 getnanotime(struct timespec *tsp)
306 struct timehands *th;
309 TC_COUNT(ngetnanotime);
312 gen = th->th_generation;
313 *tsp = th->th_nanotime;
314 } while (gen == 0 || gen != th->th_generation);
318 getmicrotime(struct timeval *tvp)
320 struct timehands *th;
323 TC_COUNT(ngetmicrotime);
326 gen = th->th_generation;
327 *tvp = th->th_microtime;
328 } while (gen == 0 || gen != th->th_generation);
332 * Initialize a new timecounter and possibly use it.
335 tc_init(struct timecounter *tc)
338 struct sysctl_oid *tc_root;
340 u = tc->tc_frequency / tc->tc_counter_mask;
341 /* XXX: We need some margin here, 10% is a guess */
344 if (u > hz && tc->tc_quality >= 0) {
345 tc->tc_quality = -2000;
347 printf("Timecounter \"%s\" frequency %ju Hz",
348 tc->tc_name, (uintmax_t)tc->tc_frequency);
349 printf(" -- Insufficient hz, needs at least %u\n", u);
351 } else if (tc->tc_quality >= 0 || bootverbose) {
352 printf("Timecounter \"%s\" frequency %ju Hz quality %d\n",
353 tc->tc_name, (uintmax_t)tc->tc_frequency,
357 tc->tc_next = timecounters;
360 * Set up sysctl tree for this counter.
362 tc_root = SYSCTL_ADD_NODE(NULL,
363 SYSCTL_STATIC_CHILDREN(_kern_timecounter_tc), OID_AUTO, tc->tc_name,
364 CTLFLAG_RW, 0, "timecounter description");
365 SYSCTL_ADD_UINT(NULL, SYSCTL_CHILDREN(tc_root), OID_AUTO,
366 "mask", CTLFLAG_RD, &(tc->tc_counter_mask), 0,
367 "mask for implemented bits");
368 SYSCTL_ADD_PROC(NULL, SYSCTL_CHILDREN(tc_root), OID_AUTO,
369 "counter", CTLTYPE_UINT | CTLFLAG_RD, tc, sizeof(*tc),
370 sysctl_kern_timecounter_get, "IU", "current timecounter value");
371 SYSCTL_ADD_PROC(NULL, SYSCTL_CHILDREN(tc_root), OID_AUTO,
372 "frequency", CTLTYPE_QUAD | CTLFLAG_RD, tc, sizeof(*tc),
373 sysctl_kern_timecounter_freq, "QU", "timecounter frequency");
374 SYSCTL_ADD_INT(NULL, SYSCTL_CHILDREN(tc_root), OID_AUTO,
375 "quality", CTLFLAG_RD, &(tc->tc_quality), 0,
376 "goodness of time counter");
378 * Never automatically use a timecounter with negative quality.
379 * Even though we run on the dummy counter, switching here may be
380 * worse since this timecounter may not be monotonous.
382 if (tc->tc_quality < 0)
384 if (tc->tc_quality < timecounter->tc_quality)
386 if (tc->tc_quality == timecounter->tc_quality &&
387 tc->tc_frequency < timecounter->tc_frequency)
389 (void)tc->tc_get_timecount(tc);
390 (void)tc->tc_get_timecount(tc);
394 /* Report the frequency of the current timecounter. */
396 tc_getfrequency(void)
399 return (timehands->th_counter->tc_frequency);
403 * Step our concept of UTC. This is done by modifying our estimate of
408 tc_setclock(struct timespec *ts)
410 struct timespec tbef, taft;
411 struct bintime bt, bt2;
413 cpu_tick_calibrate(1);
416 timespec2bintime(ts, &bt);
418 bintime_sub(&bt, &bt2);
419 bintime_add(&bt2, &boottimebin);
421 bintime2timeval(&bt, &boottime);
423 /* XXX fiddle all the little crinkly bits around the fiords... */
426 if (timestepwarnings) {
428 "Time stepped from %jd.%09ld to %jd.%09ld (%jd.%09ld)\n",
429 (intmax_t)tbef.tv_sec, tbef.tv_nsec,
430 (intmax_t)taft.tv_sec, taft.tv_nsec,
431 (intmax_t)ts->tv_sec, ts->tv_nsec);
433 cpu_tick_calibrate(1);
437 * Initialize the next struct timehands in the ring and make
438 * it the active timehands. Along the way we might switch to a different
439 * timecounter and/or do seconds processing in NTP. Slightly magic.
445 struct timehands *th, *tho;
447 u_int delta, ncount, ogen;
452 * Make the next timehands a copy of the current one, but do not
453 * overwrite the generation or next pointer. While we update
454 * the contents, the generation must be zero.
458 ogen = th->th_generation;
459 th->th_generation = 0;
460 bcopy(tho, th, offsetof(struct timehands, th_generation));
463 * Capture a timecounter delta on the current timecounter and if
464 * changing timecounters, a counter value from the new timecounter.
465 * Update the offset fields accordingly.
467 delta = tc_delta(th);
468 if (th->th_counter != timecounter)
469 ncount = timecounter->tc_get_timecount(timecounter);
472 th->th_offset_count += delta;
473 th->th_offset_count &= th->th_counter->tc_counter_mask;
474 bintime_addx(&th->th_offset, th->th_scale * delta);
477 * Hardware latching timecounters may not generate interrupts on
478 * PPS events, so instead we poll them. There is a finite risk that
479 * the hardware might capture a count which is later than the one we
480 * got above, and therefore possibly in the next NTP second which might
481 * have a different rate than the current NTP second. It doesn't
482 * matter in practice.
484 if (tho->th_counter->tc_poll_pps)
485 tho->th_counter->tc_poll_pps(tho->th_counter);
488 * Deal with NTP second processing. The for loop normally
489 * iterates at most once, but in extreme situations it might
490 * keep NTP sane if timeouts are not run for several seconds.
491 * At boot, the time step can be large when the TOD hardware
492 * has been read, so on really large steps, we call
493 * ntp_update_second only twice. We need to call it twice in
494 * case we missed a leap second.
497 bintime_add(&bt, &boottimebin);
498 i = bt.sec - tho->th_microtime.tv_sec;
503 ntp_update_second(&th->th_adjustment, &bt.sec);
505 boottimebin.sec += bt.sec - t;
507 /* Update the UTC timestamps used by the get*() functions. */
508 /* XXX shouldn't do this here. Should force non-`get' versions. */
509 bintime2timeval(&bt, &th->th_microtime);
510 bintime2timespec(&bt, &th->th_nanotime);
512 /* Now is a good time to change timecounters. */
513 if (th->th_counter != timecounter) {
514 th->th_counter = timecounter;
515 th->th_offset_count = ncount;
519 * Recalculate the scaling factor. We want the number of 1/2^64
520 * fractions of a second per period of the hardware counter, taking
521 * into account the th_adjustment factor which the NTP PLL/adjtime(2)
522 * processing provides us with.
524 * The th_adjustment is nanoseconds per second with 32 bit binary
525 * fraction and we want 64 bit binary fraction of second:
527 * x = a * 2^32 / 10^9 = a * 4.294967296
529 * The range of th_adjustment is +/- 5000PPM so inside a 64bit int
530 * we can only multiply by about 850 without overflowing, that
531 * leaves no suitably precise fractions for multiply before divide.
533 * Divide before multiply with a fraction of 2199/512 results in a
534 * systematic undercompensation of 10PPM of th_adjustment. On a
535 * 5000PPM adjustment this is a 0.05PPM error. This is acceptable.
537 * We happily sacrifice the lowest of the 64 bits of our result
538 * to the goddess of code clarity.
541 scale = (u_int64_t)1 << 63;
542 scale += (th->th_adjustment / 1024) * 2199;
543 scale /= th->th_counter->tc_frequency;
544 th->th_scale = scale * 2;
547 * Now that the struct timehands is again consistent, set the new
548 * generation number, making sure to not make it zero.
552 th->th_generation = ogen;
554 /* Go live with the new struct timehands. */
555 time_second = th->th_microtime.tv_sec;
556 time_uptime = th->th_offset.sec;
560 /* Report or change the active timecounter hardware. */
562 sysctl_kern_timecounter_hardware(SYSCTL_HANDLER_ARGS)
565 struct timecounter *newtc, *tc;
569 strlcpy(newname, tc->tc_name, sizeof(newname));
571 error = sysctl_handle_string(oidp, &newname[0], sizeof(newname), req);
572 if (error != 0 || req->newptr == NULL ||
573 strcmp(newname, tc->tc_name) == 0)
575 for (newtc = timecounters; newtc != NULL; newtc = newtc->tc_next) {
576 if (strcmp(newname, newtc->tc_name) != 0)
579 /* Warm up new timecounter. */
580 (void)newtc->tc_get_timecount(newtc);
581 (void)newtc->tc_get_timecount(newtc);
589 SYSCTL_PROC(_kern_timecounter, OID_AUTO, hardware, CTLTYPE_STRING | CTLFLAG_RW,
590 0, 0, sysctl_kern_timecounter_hardware, "A", "");
593 /* Report or change the active timecounter hardware. */
595 sysctl_kern_timecounter_choice(SYSCTL_HANDLER_ARGS)
598 struct timecounter *tc;
603 for (tc = timecounters; error == 0 && tc != NULL; tc = tc->tc_next) {
604 sprintf(buf, "%s%s(%d)",
605 spc, tc->tc_name, tc->tc_quality);
606 error = SYSCTL_OUT(req, buf, strlen(buf));
612 SYSCTL_PROC(_kern_timecounter, OID_AUTO, choice, CTLTYPE_STRING | CTLFLAG_RD,
613 0, 0, sysctl_kern_timecounter_choice, "A", "");
616 * RFC 2783 PPS-API implementation.
620 pps_ioctl(u_long cmd, caddr_t data, struct pps_state *pps)
623 struct pps_fetch_args *fapi;
625 struct pps_kcbind_args *kapi;
628 KASSERT(pps != NULL, ("NULL pps pointer in pps_ioctl"));
632 case PPS_IOC_DESTROY:
634 case PPS_IOC_SETPARAMS:
635 app = (pps_params_t *)data;
636 if (app->mode & ~pps->ppscap)
638 pps->ppsparam = *app;
640 case PPS_IOC_GETPARAMS:
641 app = (pps_params_t *)data;
642 *app = pps->ppsparam;
643 app->api_version = PPS_API_VERS_1;
646 *(int*)data = pps->ppscap;
649 fapi = (struct pps_fetch_args *)data;
650 if (fapi->tsformat && fapi->tsformat != PPS_TSFMT_TSPEC)
652 if (fapi->timeout.tv_sec || fapi->timeout.tv_nsec)
654 pps->ppsinfo.current_mode = pps->ppsparam.mode;
655 fapi->pps_info_buf = pps->ppsinfo;
659 kapi = (struct pps_kcbind_args *)data;
660 /* XXX Only root should be able to do this */
661 if (kapi->tsformat && kapi->tsformat != PPS_TSFMT_TSPEC)
663 if (kapi->kernel_consumer != PPS_KC_HARDPPS)
665 if (kapi->edge & ~pps->ppscap)
667 pps->kcmode = kapi->edge;
678 pps_init(struct pps_state *pps)
680 pps->ppscap |= PPS_TSFMT_TSPEC;
681 if (pps->ppscap & PPS_CAPTUREASSERT)
682 pps->ppscap |= PPS_OFFSETASSERT;
683 if (pps->ppscap & PPS_CAPTURECLEAR)
684 pps->ppscap |= PPS_OFFSETCLEAR;
688 pps_capture(struct pps_state *pps)
690 struct timehands *th;
692 KASSERT(pps != NULL, ("NULL pps pointer in pps_capture"));
694 pps->capgen = th->th_generation;
696 pps->capcount = th->th_counter->tc_get_timecount(th->th_counter);
697 if (pps->capgen != th->th_generation)
702 pps_event(struct pps_state *pps, int event)
705 struct timespec ts, *tsp, *osp;
706 u_int tcount, *pcount;
710 KASSERT(pps != NULL, ("NULL pps pointer in pps_event"));
711 /* If the timecounter was wound up underneath us, bail out. */
712 if (pps->capgen == 0 || pps->capgen != pps->capth->th_generation)
715 /* Things would be easier with arrays. */
716 if (event == PPS_CAPTUREASSERT) {
717 tsp = &pps->ppsinfo.assert_timestamp;
718 osp = &pps->ppsparam.assert_offset;
719 foff = pps->ppsparam.mode & PPS_OFFSETASSERT;
720 fhard = pps->kcmode & PPS_CAPTUREASSERT;
721 pcount = &pps->ppscount[0];
722 pseq = &pps->ppsinfo.assert_sequence;
724 tsp = &pps->ppsinfo.clear_timestamp;
725 osp = &pps->ppsparam.clear_offset;
726 foff = pps->ppsparam.mode & PPS_OFFSETCLEAR;
727 fhard = pps->kcmode & PPS_CAPTURECLEAR;
728 pcount = &pps->ppscount[1];
729 pseq = &pps->ppsinfo.clear_sequence;
733 * If the timecounter changed, we cannot compare the count values, so
734 * we have to drop the rest of the PPS-stuff until the next event.
736 if (pps->ppstc != pps->capth->th_counter) {
737 pps->ppstc = pps->capth->th_counter;
738 *pcount = pps->capcount;
739 pps->ppscount[2] = pps->capcount;
743 /* Convert the count to a timespec. */
744 tcount = pps->capcount - pps->capth->th_offset_count;
745 tcount &= pps->capth->th_counter->tc_counter_mask;
746 bt = pps->capth->th_offset;
747 bintime_addx(&bt, pps->capth->th_scale * tcount);
748 bintime_add(&bt, &boottimebin);
749 bintime2timespec(&bt, &ts);
751 /* If the timecounter was wound up underneath us, bail out. */
752 if (pps->capgen != pps->capth->th_generation)
755 *pcount = pps->capcount;
760 timespecadd(tsp, osp);
761 if (tsp->tv_nsec < 0) {
762 tsp->tv_nsec += 1000000000;
771 * Feed the NTP PLL/FLL.
772 * The FLL wants to know how many (hardware) nanoseconds
773 * elapsed since the previous event.
775 tcount = pps->capcount - pps->ppscount[2];
776 pps->ppscount[2] = pps->capcount;
777 tcount &= pps->capth->th_counter->tc_counter_mask;
778 scale = (u_int64_t)1 << 63;
779 scale /= pps->capth->th_counter->tc_frequency;
783 bintime_addx(&bt, scale * tcount);
784 bintime2timespec(&bt, &ts);
785 hardpps(tsp, ts.tv_nsec + 1000000000 * ts.tv_sec);
791 * Timecounters need to be updated every so often to prevent the hardware
792 * counter from overflowing. Updating also recalculates the cached values
793 * used by the get*() family of functions, so their precision depends on
794 * the update frequency.
798 SYSCTL_INT(_kern_timecounter, OID_AUTO, tick, CTLFLAG_RD, &tc_tick, 0, "");
804 static time_t last_calib;
806 if (++count < tc_tick)
810 if (time_uptime != last_calib && !(time_uptime & 0xf)) {
811 cpu_tick_calibrate(0);
812 last_calib = time_uptime;
817 inittimecounter(void *dummy)
822 * Set the initial timeout to
823 * max(1, <approx. number of hardclock ticks in a millisecond>).
824 * People should probably not use the sysctl to set the timeout
825 * to smaller than its inital value, since that value is the
826 * smallest reasonable one. If they want better timestamps they
827 * should use the non-"get"* functions.
830 tc_tick = (hz + 500) / 1000;
833 p = (tc_tick * 1000000) / hz;
834 printf("Timecounters tick every %d.%03u msec\n", p / 1000, p % 1000);
836 /* warm up new timecounter (again) and get rolling. */
837 (void)timecounter->tc_get_timecount(timecounter);
838 (void)timecounter->tc_get_timecount(timecounter);
841 SYSINIT(timecounter, SI_SUB_CLOCKS, SI_ORDER_SECOND, inittimecounter, NULL);
843 /* Cpu tick handling -------------------------------------------------*/
845 static int cpu_tick_variable;
846 static uint64_t cpu_tick_frequency;
851 static uint64_t base;
852 static unsigned last;
854 struct timecounter *tc;
856 tc = timehands->th_counter;
857 u = tc->tc_get_timecount(tc) & tc->tc_counter_mask;
859 base += (uint64_t)tc->tc_counter_mask + 1;
865 * This function gets called ever 16 seconds on only one designated
866 * CPU in the system from hardclock() via tc_ticktock().
868 * Whenever the real time clock is stepped we get called with reset=1
869 * to make sure we handle suspend/resume and similar events correctly.
873 cpu_tick_calibrate(int reset)
875 static uint64_t c_last;
876 uint64_t c_this, c_delta;
877 static struct bintime t_last;
878 struct bintime t_this, t_delta;
882 /* The clock was stepped, abort & reset */
887 /* we don't calibrate fixed rate cputicks */
888 if (!cpu_tick_variable)
891 getbinuptime(&t_this);
892 c_this = cpu_ticks();
893 if (t_last.sec != 0) {
894 c_delta = c_this - c_last;
896 bintime_sub(&t_delta, &t_last);
898 * Validate that 16 +/- 1/256 seconds passed.
899 * After division by 16 this gives us a precision of
900 * roughly 250PPM which is sufficient
902 if (t_delta.sec > 16 || (
903 t_delta.sec == 16 && t_delta.frac >= (0x01LL << 56))) {
906 printf("t_delta %ju.%016jx too long\n",
907 (uintmax_t)t_delta.sec,
908 (uintmax_t)t_delta.frac);
909 } else if (t_delta.sec < 15 ||
910 (t_delta.sec == 15 && t_delta.frac <= (0xffLL << 56))) {
913 printf("t_delta %ju.%016jx too short\n",
914 (uintmax_t)t_delta.sec,
915 (uintmax_t)t_delta.frac);
920 * 2^(64-20) / 16[s] =
922 * 17.592.186.044.416 / 16 =
923 * 1.099.511.627.776 [Hz]
925 divi = t_delta.sec << 20;
926 divi |= t_delta.frac >> (64 - 20);
929 if (c_delta > cpu_tick_frequency) {
930 if (0 && bootverbose)
931 printf("cpu_tick increased to %ju Hz\n",
933 cpu_tick_frequency = c_delta;
942 set_cputicker(cpu_tick_f *func, uint64_t freq, unsigned var)
946 cpu_ticks = tc_cpu_ticks;
948 cpu_tick_frequency = freq;
949 cpu_tick_variable = var;
958 if (cpu_ticks == tc_cpu_ticks)
959 return (tc_getfrequency());
960 return (cpu_tick_frequency);
964 * We need to be slightly careful converting cputicks to microseconds.
965 * There is plenty of margin in 64 bits of microseconds (half a million
966 * years) and in 64 bits at 4 GHz (146 years), but if we do a multiply
967 * before divide conversion (to retain precision) we find that the
968 * margin shrinks to 1.5 hours (one millionth of 146y).
969 * With a three prong approach we never lose significant bits, no
970 * matter what the cputick rate and length of timeinterval is.
974 cputick2usec(uint64_t tick)
977 if (tick > 18446744073709551LL) /* floor(2^64 / 1000) */
978 return (tick / (cpu_tickrate() / 1000000LL));
979 else if (tick > 18446744073709LL) /* floor(2^64 / 1000000) */
980 return ((tick * 1000LL) / (cpu_tickrate() / 1000LL));
982 return ((tick * 1000000LL) / cpu_tickrate());
985 cpu_tick_f *cpu_ticks = tc_cpu_ticks;